1. Field of the Invention
This invention relates generally to a biopsy instrument, and more particularly to an improved apparatus for performing soft tissue biopsy.
2. Discussion of the Prior Art
In the “Background of the Invention” section of U.S. Pat. No. 5,036,860, there is set forth a discussion of prior art soft tissue biopsy devices and the shortcomings of those devices. The contents of U.S. Pat. No. 5,036,860 are hereby incorporated by reference as if set forth in full herein.
The preferred embodiment of the invention described in the '860 patent comprises an elongated housing having somewhat the shape of a ballpoint pin and with a small opening at one end. A first and hollow cannula is positioned within the housing and is reciprocally moveable. One end of the first cannula extends through the opening in the elongate housing and has a sharpened tip for insertion into tissue from which a biopsy specimen is to be taken. A needle-like stylet is positioned within the first cannula and is reciprocally moveable within the lumen of the first cannula. The needle has a sharpened tip for facilitating insertion into tissue and proximate the sharpened tip is a notch or recess into which the tissue specimen projects when the needle is inserted into soft tissue.
The needle stylet is mounted in a slide, allowing it to move independently of the first, outer cannula. A spring and latch mechanism is provided that allows the needle and cannula combination to be placed in a cocked position. Once the device is cocked, it is inserted into the soft tissue from which a specimen is to be withdrawn and the device is “fired”. In a two-step sequence, the needle stylet is first returned to its uncocked position and then the outer cannula also is advanced to slide over and sever the biopsy sample from surrounding tissue and to capture the specimen contained in the stylet's notch as the needle and first cannula are simultaneously withdrawn from the target tissue.
During a soft tissue biopsy procedure, it is often desirable to collect multiple samples proximate a suspected tumor or the like. In the prior art devices described in the '860 patent, only a single sample can be taken for any one penetration of tissue by the outer cannula. This is because the outer cannula and the stylet housed therein must be removed from the patient before a first sample can be released for microscopic examination. Thus, it would be advantageous to have a soft tissue biopsy device that would allow multiple samples to be extracted from the patient without having to create multiple puncture wounds, thereby reducing patient trauma.
PCT International Publication WO 96/04851 describes a biopsy instrument that is designed to be fired twice to collect two biopsy specimens in a notched stylet without removing the instrument from the patient's body. However, it has no provision for adjusting the length of the multiple specimens. They are each necessarily of the same length.
While prior art biopsy devices of the type described have permitted adjustment of the sample size to be excised, none, so far as is known, has allowed multiple samples of different sizes to be extracted without having to make multiple punctures with the cannula.
In the prior art arrangement described in the '860 patent, the release of a spring force for driving the sampling stylet results in the triggering of the outer cannula as the stylet reaches its end of travel point. It would be advantageous in an instrument of the type described if the outer cannula movement can be made independent of stylet firing if so desired in a fully automated device.
Then, too, it is important that the soft tissue biopsy instrument provide for one-handed operation and that it be safe to use, having suitable interlocks for preventing premature, unintended firing of the stylet and/or outer cannula.